It has been estimated that for vehicle-to-pedestrian collisions eighty percent of serious injuries occur to the pedestrian's head. (Crandall et al., “Designing Road Vehicles for Pedestrian Protection,” BMJ [formerly British Medical Journal], 324 [7346], pp. 1145-1148)
When impacted by a vehicle, a pedestrian's head may strike the vehicle's engine hood or windshield glass. Given the importance of minimizing injury to the pedestrian in pedestrian-vehicle impacts, pedestrian protection has become a goal of the United Nations Economic Commission for Europe. The UNECE advanced a proposal “to develop a global technical regulation concerning the protection of pedestrians and other vulnerable road users in collision with vehicles and final report on the development of the global technical regulation concerning pedestrian safety.” Along with the Global Technical Regulation No. 9 (GTR-9), the European New Car Assessment Programme (Euro NCAP) developed a pedestrian protection star rating system. Vehicle manufacturers must meet child head, adult head, upper leg and lower leg test requirements provided to assess vehicle designs for mitigation of pedestrian injury caused by a vehicle frontal impact.
For laboratory testing evaluation, a pedestrian head form impact zone grid covering portions of the hood and windshield is defined as shown in FIG. 1 (http://www.euroncap.com/files/Euro-NCAP-Pedestrian-Protocol-v6.1-0-f2bd8d69-18e5-4779-9829-86a07299ae7e.pdf) and FIG. 2. The grid area on the windshield just rearward of the hood, generally above the cowl, is a challenging area for pedestrian protection due to the individual and collective stiffness of a variety of interior and exterior components adjacent or interfacing one another, such as a cowl, wipers, wiper motors, future vehicle hardware content and the like, as illustrated in FIG. 3.
In an effort to reduce injury to the pedestrian's head in a pedestrian-vehicle impact event, automotive engineers developed systems in which the trailing edge of the vehicle engine hood is raised through a variety of available lift mechanisms to provide earlier occupant head pick-up, additional head “ride-down” distance and enhanced energy dissipation through deformation of the elevated hood. However, while “hood lifting” technology provides some benefit to a struck pedestrian, such technologies do not address the vehicles stiffness rearward of the hood in the area of the windshield above instrument panel and cowl. Available countermeasures to reduce stiffness behind the hood or above the cowl include cowl airbags, softer instrument panel and foam covers at the cowl. These countermeasures can be costly, provide limited effectiveness and impose various design and appearance challenges.
Accordingly, there is a need for a practical and effective system to protect pedestrians in a pedestrian-vehicle impact event. As in so many areas of vehicle technology, there is room for improvement related to the protection of pedestrians in a pedestrian-vehicle impact event.